The present invention relates to inking systems for web printing presses, and more particularly, to several improved systems for operating the rotary ink pumps which are used in such presses.
For example, a typical press may include 24 ink pumps which operate to print twenty-four zones. Each pump supplies the ink to one zone of printing, and as a consequence, the ink pumps are fairly closely spaced apart from each other. Because the requirements for printing mean that any one zone may have the same, similar, or quite different ink requirements than any other zone, the ink pump system must accommodate these different requirements. The ink pumps used in these presses are rotary pumps, for example, of the type described in U.S. Pat. No. 5,482,448, issued Jan. 9, 1996. A different ink pump is also shown in U.S. Pat. No. 5,472,324, issued Dec. 5, 1995. Either kind of pump, or other kinds of pumps, may be used with the drive systems described. The contents of both of these patents are hereby incorporated fully herein by reference.
The novel features of the present invention include the manner in which these ink pumps are driven. This manner and the structure of the various drive mechanisms are contained in, and set out more fully in, the following detailed description. Several different mechanisms are described in detail, but they all have in common the fact that there is generally a stop-start or intermittent rotary motion of the pumps. The input varies, but includes rotary or oscillatory motion. The different mechanisms all include an amplitude adjustment which then results in a variable angular displacement of the shafts of the ink pumps.
In one case, which involves two pumps, the variable stroke motion is achieved by a single, bidirectional stepper motor and a pair of overrunning clutches for each ink pump. In this first embodiment, there are a pair of pumps which are driven by a novel drive mechanism. The pumps are arrayed in pairs but the two pumps are driven in an opposite hand of rotation by a stepper motor and two drive shafts.
The stepper motor operates the two shafts, one in a first direction and the second in an opposite direction, with variable angular displacement. This is accomplished by positioning the overrunning clutches in an opposite sense, with one of the clutches being placed in one driving mechanism while the opposite one is driven by a clutch operating in a different direction. In both cases, these are two overrunning clutches for each shaft, a dynamic clutch and a holding clutch. The holding clutch always maintains pressure on the pump drive, because the ink must be held under pressure as soon as the piston completes its stroke.
This construction has the advantage of using only one motor for two pumps, and besides energy savings and related advantages, this enables the motors to be closely spaced apart so the pumps can likewise be spaced closely apart. Thus, in a 24-pump application, there need be only twelve motors.
In all applications, there is also a dynamic overrunning clutch and a holding clutch which is used during the reset period of the shaft. The pistons pump ink in one direction only so each pump shaft is driven in only one direction. In all of the constructions, the angular displacement over time of the pump drive shaft is varied to change the rate at which the ink is delivered.
It is therefore an object of the present invention to provide a series of mechanisms which, although differing somewhat in the manner in which they operate, have the same or approximately the same way of driving the shaft(s) of the ink pump.
Another object of the present invention is to provide a bidirectional stepper motor which steps or operates in two different directions, and hence a single motor can be used to drive two ink pumps, thereby reducing by half the number of motors used.
A further object of the present invention is to use a novel means for driving paired ink pumps, one of which rotates in one direction and the other which rotates in the opposite direction.
A still further object of the invention is to provide a drive for plural ink pumps, each one of which contains two clutches in the drive shaft mechanisms, with one being a dynamic clutch which allows the drive shaft to move in a certain rotary position, and a holding clutch preventing the drive shaft from rotating backwards under the accumulated pressure.
A further object is to provide a series of novel constructions for operating ink pumps having a pair of pump elements concentrically arranged within a ported sleeve, with both of the elements operating to provide a full cycle of ink being pumped.
Another object is to provide several novel systems and arrangements for driving rotary ink pumps.
A still further object of the invention is to provide a stepper motor which will drive two sprockets, one in each direction, and which can have the same or completely different driving “information” for each direction of rotary displacement.
A further object of the invention is to provide an ink pump system wherein a single pump drives a pair of pump snails by means of a toothed belt or the like.
A still further object of the invention is to provide a plurality of different pump drive mechanisms, wherein an intermittent rotary motion is provided in one direction for the pump shaft.
A further object is to provide a mechanism for converting the rotary motion on the belt or other drive means to an intermittent rotary motion by changing the amplitude of the intermittent motion which rotates the drive shaft.
Another object is to provide a mechanism wherein the primary drive comes from a motor driving a reciprocating drive rod, with the reciprocating drive rod providing the motion for a series of ink pumps.
Another object is to provide a mechanism wherein there are three shafts required so as to achieve unidirectional rotary motion in the first and third drive shafts, and wherein the second shaft can be made to undergo a slightly aphasia motion for the output shaft.
Another object is to provide a pump drive system which includes three shafts, with the difference in angular position of the first and third shafts used to provide an intermittent movement of the second shaft such that, when the two shafts are in phase, the center shaft will not move but when they are out of phase, the center shaft undergoes a swinging intermittent motion which is imparted to the pump drive shafts.
A still further object of the invention is to provide a drive system which is operated by belts or pulleys and in which a bifurcated drive shaft is used, with the shaft being off settable equally at the top and bottom with the consequent neutralizing of the offset. In this construction, the pump drive also has a pair of one-way clutches.
Another object is to provide a drive yoke with the centerline of a threaded shaft being equally offset from the circular locus of the groove, thereby neutralizing the offset.